Hello Gents (sorry for the generalization to an women in the audience),

91 S4 wont start after the following:

• Top End Refresh including knock sensors, some vacuum connectors, MAF clean, gaskets, flappy valve and bearings
• Powder coat intake and covers (not throttle body)
• 24# injectors (new)
• Caps, rotors, plugs, coil to cap wires
• Porken chips bought new for the car

After the above, the car started and ran really crappy (no power). Drove down the street and back with no improvement.
Started again and had a tough time maintaining idle then died. Will not start since.

I have fuel (no guage but pressure seems strong with rail port removed)
I have spark on both sides (checked with inductive timing light and with plug on block to see spark)
I fee popping in injectors with hand on them so I think they are firing
I went back to original chips
I tested the LH module in another car
Refitted the intake to ensure seated well
Removed and checked plugs, gaps, etc)
Removed and refit caps and rotors (thinking maybe I got them out of phase but learned they will only go on 1 way)
Confirmed that timing belt is not broken and cams are turning.
Battery on a charger (even swapped with another car to make sure)
Checked main plug for corrosion (none at all)
Tried to start with Ether (starting fluid) sprayed in MAF screen - No ignition at all
Tried to start with foot pedal all the way depressed
Don't think Temp II sensor cable bad
Checked all fuses
Checked AZ, LH, and Fuel Pump relays in horn position (beep beep)

It does not even act like it wants to start. The car was running pretty well prior to above action. The knock sensors were not good, but otherwise it wall all PM.

I have read many of the other no-start threads.
Not sure what to try next.

Your comments are appreciated. Thank you.

 

Did you perhaps clean the two main grounds at the back on the block while you had the intake off? Did they get connected back correctly? Is the connector for the Crank Position Sensor properly seated?

Mike

 

I did not clean the grounds (probably should have) and did not remove the CPS.
I think I seated the CPS connector well but now sure since I think it is under the intake unless I am mistaken?

If CPS is not seated I should get no spark, right?

Thanks

 

Check that the coil wires are fully seated.

 

I have reseated. I have spark at the plugs on both sides.

 

Sounds flooded... What was the time interval between running-crappy and dying, and refusing to start again? If the mixture was very rich for some reason, then the engine would tend to flood. Once flooded, they are very hard to restart until things dry out.

Pull a couple of plugs and have a look: Wet? Smell like gas? Do you smell gas in the exhaust tips after cranking for 5-10 seconds?

The fix is either (a) have a few beers and try tomorrow, or (b) pull the fuel-pump relay, crank 10-15 seconds with pedal all the way down (i.e. no fuel and lots of air), wait 30-60 seconds (for starter to cool) and repeat. If it is flooded then at some point it will sputter and try to start, then die again from lack of fuel. Replace FP relay and go from there.

Going back to stock chips with 24# injectors is going to be way too rich. To "undo" that mod requires swapping back to 19# injectors to go along with the factory LH chip. Before doing that I would seek guidance from the chip vendor, I am sure Ken offers support for chip-related issues.

The mystery is why it ran crappy in the first place. If rich, why? Give the MAF a careful eyeball, and make sure that the hot-wire survived the cleaning. It's pretty delicate. There are also some resistance checks for temp-II etc which are outlined in the WSM. But none of that sounds like the issue.

The elephant in the room of course is the powder-coated intake. Are you sure that it was thoroughly cleaned after being blasted and PC'ed? It would not be a bad idea to run a compression test.

Good hunting, and keep posting!

 

Given the symptoms it could be a massive air leak. Are all the hoses connected to the manifold? Is the MAF sensor fully seated in the elbow? Is the MAF connector connected properly? Pictures of the engine might help.

 

Did you powder coat the water bridge? If so it could have a bad ground to the temp2 causing issues. Did you have the plug wires off? If so are you 100% certain the firing order is correct?

 

Addressing the questions in order:

Re: Flooding - I have been working on the issue for more than a week now. Numerous days and no start. I don't think it is flooding or it would try to start at least in the beginning.

I have gone back to the Porken chips. I don't think that they are the problem.

The MAF is well connected (bith electrically and at the elbow) - But I think a bad MAF would cause poor running - not a total no start?

The powder coating question - well I don't even want to think about that one....

Massive air leak - I agree, but from where? The hoses are connected and tight. New vacuum connectors for the most part - but the old ones were in very good condition anyway.

Did not coat the water bridge (or even touch it). So no ground issues there.

The firing order has been checked and rechecked - I even tool the wires, cap and rotor off to make sure it was all seated well.

I don't get it - I have all the conditions of running and no start. I have to be missing something rather big in the equation. I am not sure why it will not start.

Keep the ideas coming. I may have to pull the intake again to check the CPS connection and cleaning of the grounds unless someone has another idea to check/try.

I do have the air filter (the whole air canister) off. Car is breathing straight through the top side of the MAF - I cant imagine that this would matter? I have tried with the filter in place also but left it off for simplicity.

Thanks for your responses. They are all appreciated.

 

You can do a smoke test for the air leak.

This can be done with a proper "smoke tester", or simply by taking a vacuum line that goes into the intake and lighting up a cigar. You then blow smoke into the vacuum line, into the intake and out any leaks.

You might still want to pull the plugs & check them, even if you don't think you are flooding. They may provide a clue.

 

Depending on the failure mode of the MAF it could be the culprit. Disconnect the plug and see if it will start. Helped troubleshoot an 86 that wouldn't start or run that ended up being the MAF. The car wouldn't start or run with the MAF connected but would if you unplugged it.

Mike

 

Trey - did you clean the intake fully after the powder coating??? I am with Jim about the elephant in the room - I hope I am wrong.

When we tested the brain did it have Ken's chips or stock chips?

Is the car still turning over slowly? Have you tried a different battery that is fully charged?

 

Does that car have spark ? That is the first step in methodically troubleshooting a no start.

 

You don't need to pull the intake to access the CPS, just the MAF. If you didn't replace that when doing the top end you should now. It's an old part and is a wear item.

 

I'm a little surprised to read that it does have spark.
If it is sparking, then I would expect it to at least sputter and try to start on the ether.

And with all the cranking you're doing, you'd surely smell fuel if the injectors were firing.
So it sounds like you're not getting any fuel.

I believe the lack of a signal from the CPS will prevent both spark and fuel.

If you're certain you're getting spark, then the focus needs to be on why no fuel...